The invention relates to an image processing method belonging to a sequence of at least two images having a surface representing an organ or a part of an organ which is deformable over time and referred to as an organ surface, said surface including characteristic points, denoted marking points, which correspond to each other from one image to another in the sequence. This invention also relates to an image processing apparatus for implementing the method described above.
The invention finds its application in the field of medical image processing. The method is in particular applicable to organ images marked by magnetic resonance spatial modulation. This marking is visible on the images in the form of marking lines with points of intersection. The marking lines deform following the deformation of the organ. Said intersection points are then chosen as marking points since the matches between these points from one image to another are easily detectable.
An organ image processing method marked by magnetic modulation with a view to quantifying the deformation of the organ is already known from the state of the art through the publication by Matthias Stuber et al. entitled “Quantification of the local heartwall motion by magnetic resonance myocardial tagging”. In this document, the points of intersection between the marking lines are determined by approximation algorithms based on a calculation of potential (“snakes”). In addition, this method uses a mean of the angles with respect to the center of gravity in order to quantify the rotation and contraction.
This method has drawbacks. First of all, the use of approximation algorithms based on a calculation of potential for determining the points of intersection between the marking lines lacks precision. Then the use of the mean of the angles with respect to the center of gravity for quantifying the rotation and contraction also leads to a result which is imprecise and mathematically incorrect. Consequently subsequent extrapolations are not reliable for the points other than the marking points. However, such extrapolations are necessary when it is wished to follow the movement of a particular structure per unit length which is defined on an image and which is made to deform with the organ in the sequence of images.